Fuel injection valve and method for the production of a valve needle for a fuel injection valve

ABSTRACT

A fuel injection valve that possesses an axially movable valve needle which includes at least one armature and one spherical valve closure element. The armature forms a closure element support which is joined at its downstream end to the valve closure element. The end of the closure element support facing toward the valve closure element is deformed in such a way that a polygonal profile is present. In accordance with the number of profile edges, at least two flowthrough openings, communicating with an inner longitudinal bore, are formed between the closure element support and the surface of the valve closure element, through which openings fuel can easily flow.

BACKGROUND INFORMATION

The present invention is based on a fuel injection valve, and on amethod for manufacturing a valve needle of a fuel injection valve.

A fuel injection valve in which a valve needle is constituted from anarmature, a tubular joining part, and a spherical valve closure elementis already known from German Published Patent Application 38 31 196 orGerman Published Application Patent no. 40 08 675. The armature and thevalve closure element are joined to one another via the tubular joiningelement, the joining part, to which the valve closure element isimmovably joined via a weld bead, serving as the immediate closureelement support. The joining part has a plurality of transverselyextending flow openings through which fuel can emerge from an internalpassthrough opening and flow, outside the joining part, to the valveclosure element and to a valve seat surface coacting with the valveclosure element. In addition, the joining tube has a longitudinal slit,extending over the entire length, through which, because of its largehydraulic flow cross section, fuel arriving from the inner passthroughopening can flow very quickly. Most of the fuel to be discharged alreadyflows out of the joining part over its length. The remaining quantityemerges directly from the joining part only upon reaching the sphericalsurface, so that when viewed over the joining region between joiningpart and valve closure element, which extends over 360 degrees, there isa definite inhomogeneity in fuel distribution.

SUMMARY OF THE INVENTION

The fuel injection valve according to the present invention, has theadvantage that opportunities for fuel flow at the valve needle can becreated in economical, reliable, and particularly simple fashion. Thevalve needle includes at least one closure element support and one valveclosure element. The closure element support is shaped, at its endfacing the valve closure element, in a manner which deviates from anannular profile such that at least two flowthrough openings are formedbetween the closure element support and the surface of the valve closureelement, through which fuel arriving from an inner longitudinal bore canflow unimpeded toward a valve seat surface. In particularly simplefashion, the downstream end of the closure element support isplastically deformed by deformation tools from an annular profile into apolygonal profile. Optimum flow to the metering region of the valve isthus achieved with little production outlay.

Advantageously, the fuel flows to the surface of the valve closureelement in the interior of the closure element support. As compared withknown valves, this eliminates transverse openings and slits in theclosure element support, which are otherwise needed for the fuel toemerge from the internal sleeve opening of the closure element support.Also eliminated are the machining problems (e.g. deburring) associatedwith such transverse openings.

In particularly advantageous fashion, the valve closure element is ofspherical configuration, so that centering of the valve closure elementon the closure element support is particularly easy.

The polygonal profile of the closure element support has an equal numberof angle regions and edge regions, corresponding to the number offlowthrough openings. A triangular profile results in the bestcompromise between the greatest possible open cross section for the sumof the flowthrough openings and good centering of the valve closureelement on the closure element support. Great variability in theindividual profiles of the closure element support can be created byusing different deformation tools.

In particularly advantageous fashion, the armature can itself servedirectly as the closure element support, so that together with the valveclosure element a two-part valve needle is present. A valve needle ofthis kind is particularly easy and economical to manufacture, andbecause of the reduced parts count has only the join to be made betweenthe valve closure element and closure element support.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a fuel injection valve according to the present invention.

FIG. 2 shows an armature, serving as closure element support, with adeformation tool.

FIG. 3 shows a two-part valve needle.

FIG. 4 shows a section through a closure element support with atriangular profile, along line IV—IV in FIG. 3.

FIG. 5 shows a section through a closure element support with apentagonal profile.

FIG. 6 shows a tripartite valve needle.

FIG. 7 shows a first illustration of a valve closure element thatdeviates from a spherical shape and can be mounted on a closure elementsupport.

FIG. 8 shows a second illustration of a valve closure element thatdeviates from a spherical shape and can be mounted on a closure elementsupport.

FIG. 9 shows a third illustration of a valve closure element thatdeviates from a spherical shape and can be mounted on a closure elementsupport

DETAILED DESCRIPTION

The valve according to the present invention depicted in the form of anelectromagnetically actuable fuel injection valve for fuel injectionsystems of mixture-compressing, spark-ignited internal combustionengines, has a largely tubular core 2 which is surrounded by a magnetcoil 1 and serves as internal pole and partly as a fuel passage.Together with an upper disk-shaped cover element 3, core 2 makespossible a particularly compact configuration of the injection valve inthe region of magnet coil 1. Magnet coil 1 is surrounded by an externalferromagnetic valve shell 5 constituting the external pole, whichcompletely surrounds magnet coil 1 in the circumferential direction andis immovably joined at its upper end to cover element 3, e.g. by a weldbead 6. To close the magnetic circuit, valve shell 5 is embodied instepped fashion at its lower end, thus forming a guide segment 8 which,similarly to cover element 3, axially encloses magnet coil 1 andrepresents the boundary of magnet coil region 1 toward the bottom or inthe downstream direction.

Guide segment 8 of valve shell 5, magnet coil 1, and cover element 3form an internal opening 11 and 58, running concentrically with alongitudinal valve axis 10, in which an elongated sleeve 12 extends. Aninner longitudinal opening 9 of ferritic sleeve 12 serve partly as guideopening for a valve needle 13 that is axially movable along longitudinalvalve axis 10. Sleeve 12 is therefore produced in dimensionally accuratefashion with respect to the inside diameter of internal opening 9.Viewed in the downstream direction, sleeve 12 ends, for example, in theregion of guide segment 8 of valve shell 5, to which it is immovablyjoined, for example, with a weld bead 54. The stationary core 2 is alsoarranged in longitudinal opening 9 of sleeve 12 outside the axiallymovable valve needle 13. In addition to receiving core 2, sleeve 12 alsoperforms a sealing function, so that magnet coil 1 present in theinjection valve is dry. This is also achieved by the fact that thedisk-shaped cover element 3 completely covers magnet coil 1 on its upperside. Inner opening 58 in cover element 3 makes it possible to configuresleeve 12 and thus also core 2 in elongated fashion, so that bothcomponents pass through opening 58 and project beyond cover element 3.

Adjoining the lower guide segment 8 of valve shell 5 is a valve seatelement 14 which has a fixed valve seat surface 15 constituting a valveseat. Valve seat element 14 is immovably joined to valve shell 5, by wayof a second weld bead 16 produced, for example, with a laser. Valveneedle 13 is constituted by a tubular armature 17 and a, for example,spherical valve closure element 18 joined immovably thereto, armature 17serving directly as the closure element support. Valve closure element18 has on its circumference, for example, five flattened areas 23 whichallow fuel to flow past valve closure element 18 to valve seat surface15. Arranged at the downstream end face of valve seat element 14, forexample in a depression 19, is a flat perforated spray disk 20, theimmovable joining between valve seat element 14 and perforated spraydisk 20 being attained, for example, using a peripheral sealed weld bead21.

Actuation of the injection valve is accomplished, in known fashion,electromagnetically. The electromagnetic circuit having magnet coil 1,inner core 2, outer valve shell 5, and armature 17 serves to move valveneedle 13 axially, and thus to open the injection valve against thespring force of a return spring 25 and to close it. Armature 17 facestoward core 2 with its end which faces away from valve closure element18.

The spherical valve closure element 18 coacts with valve seat surface 15of valve seat element 14, that surface tapering in truncated conicalform in the flow direction and being configured in valve seat element 14axially downstream of a guide opening 26. Perforated spray disk 20possesses at least one, for example four spray openings 27 shaped byelectrodischarge machining or punching.

The depth to which core 2 is inserted in the injection valve governs,inter alia, the linear stroke of valve needle 13. The one end positionof valve needle 13, when magnet coil 1 is not energized, is defined bycontact of valve closure element 18 against valve seat surface 15 ofvalve seat element 14, while the other end position of valve needle 13,when magnet coil 1 is energized, results from contact of armature 17against the downstream end of core 2. Linear stroke adjustment isperformed by axial displacement of core 2 in sleeve 12, which, inaccordance with the desired position, is then immovably joined to sleeve12, a laser weld being useful for producing a weld bead 22.

In addition to return spring 25, an adjusting sleeve 29 is inserted intoa flow bore 38 of core 2 which runs concentrically with longitudinalvalve axis 10 and serves to convey fuel toward valve seat surface 15.Adjusting sleeve 29 serves to adjust the spring preload of return spring25, which rests against adjusting sleeve 29 and in turn is braced at itsopposite end against a shoulder 28 of armature 17; the dynamic spraydischarge volume is also adjusted using adjusting sleeve 29.

An injection valve of this kind is characterized by its particularlycompact configuration, resulting in a very small, manageable injectionvalve whose valve shell 5 has, for example, an outside diameter of onlyapproximately 11 mm. The components so far described form a preassembledindependent assembly which can be referred to as functional part 30. Thecompletely adjusted and assembled functional part 30 has, for example,an upper end surface 32 beyond which, for example, two contact pins 33project. By way of electrical contact pins 33, which serve as electricalconnecting element, electrical contact is made to magnet coil 1 and itis thereby energized.

A functional part 30 of this kind can be joined to a connector part (notdepicted), which is characterized principally in that it comprises theelectrical and hydraulic connection to the injection valve. A hydraulicconnection between the connector part (not depicted) and functional part30 is achieved, when the injection valve is completely assembled, by thefact that flow bores of the two assemblies are brought together so as toensure that fuel can flow through unimpeded. In this context, forexample, end surface 32 of functional part 30 rests directly against alower end surface of the connector part, and is immovably joinedthereto. When the connector part is mounted onto functional part 30, theportion of core 2 and of sleeve 12 projecting beyond end surface 32 can,in order to increase connection stability, project into a flow bore ofthe connector part. For secure sealing, a sealing ring 36, for example,is provided in the joining region, resting on end surface 32 of coverelement 3 and surrounding sleeve 12. In the completely assembled valve,contact pins 33 serving as electrical connection elements participate ina secure electrical connection with corresponding electrical connectionelements of the connector part.

FIG. 2 shows armature and closure element support 17, at a larger scalethan in FIG. 1, with a deformation tool 40 and 41. The tubular armatureserving as closure element support 17 is embodied, for example, as aturned part which possesses, in addition to an inner longitudinal bore45 that is stepped thanks to shoulder 28, a stepped outer contour aswell. Closure element support 17, made for example from a ferriticmaterial (e.g. 13% chromium steel), has an upper stop surface 42, facingcore 2, which is equipped with a wear protection layer, i.e. ischrome-plated. Shaped out of the external periphery of closure elementsupport 17, in a larger-diameter first segment 47, is, for example, anannular guide surface 43 which serves to guide the axially movable valveneedle 13 in sleeve 12. Analogously to shoulder 28 in inner longitudinalbore 45, a step 46 is provided on the outer contour, resulting in areduction in cross section in a second segment 48 when viewed in thedownstream direction. Larger- and smaller-diameter segments 47 and 48each initially possess a circular cross section.

According to the present invention, the annular cross section of the endof closure element support 17 facing the spherical valve closure element18, i.e. in the exemplary embodiment that of segment 48 shown in FIG. 2,is changed into a cross section which has at least two corners 60 andedges 61 (FIG. 4). Corners 60 and edges 61 do not by any means, however,need to be sharp-edged or straight. Instead, corners 60 can be roundedand edges 61 can be curved, i.e. bulging. In order to obtain a profileof this kind which deviates from a hollow cylindrical shape, a plasticdeformation of the joining region, at which valve closure element 18that is to be mounted is later attached, is performed in segment 48. Asalready indicated in FIG. 2 with the two deformation tools 40 and 41,there are two possibilities for deforming closure element support 17 atits lower segment 48 facing toward valve closure element 18. The firstdeformation possibility lies in introducing a deformation tool 40 intothe inner longitudinal bore 45 in segment 48 and performing a desireddeformation of segment 48 from the inside. The second deformationpossibility provides for allowing a deformation tool 41 to act on theouter periphery of segment 48 in order to achieve a desired deformationof segment 48. In addition, for example, it is possible also tointroduce a shaping punch into the inner longitudinal bore 45 and applyto the outer periphery a deformation tool 41 with which the contour ofthe shaping punch is reproduced in segment 48.

After the deformation of segment 48 of closure element support 17,spherical valve closure element 18 is immovably attached to thisdeformed segment 48, thus completing the axially movable valve needle13, as is evident from FIG. 3. Valve closure element 18 is joined to therespective edge regions 61′ of the deformed profile; as is desired,immovable joins cannot be made in corner regions 60′. The immovablejoins between closure element support 17 and valve closure element 18are created, for example, by way of weld beads 63 produced with a laser,the number of weld beads 63 corresponding exactly to the number of edgeregions 61′.

The formation of corner regions 60′ results in the creation of regionsat the downstream end of segment 48 which do not rest against thesurface of valve closure element 18. The result of the plasticdeformation of segment 48 has thus been to create at corner regions 60′flowthrough openings 65 through which, in particularly favorablefashion, fuel arriving from longitudinal bore 45 flows toward valve seatsurface 15. This embodiment of valve needle 13 allows fuel to flow invery simple fashion to the metering region of the injection valve.

FIG. 4 is a sectioned depiction of a section along line IV—IV in FIG. 3which illustrates in particularly descriptive fashion corner s 60 andedges 61 of closure element support 17, and flowthrough openings 65,after the attachment of valve closure element 18. It is particularlyadvantageous to use deformation tools 40, 41 with shaping punches withwhich a triangular profile can be produced. The three corner regions 60′and three edge regions 61′ in the profile of segment 48 result in threeflowthrough openings 65. Valve closure element 18 is attached to edgeregions 61′ with three weld beads 63. A triangular profile yields thebest compromise between the greatest possible open cross section for thesum of flowthrough openings 65, and good centering of valve closureelement 18 on closure element support 17. In addition to a triangularprofile, however, profiles with two, four, five (FIG. 5), or possiblyeven more corners 60 and edges 61 are also conceivable for closureelement support 17.

FIG. 6 depicts a second exemplary embodiment of a valve needle 13 inwhich parts which remain the same as or operate identically to those inthe exemplary embodiment depicted in FIG. 3 are identified by the samereference characters. Valve needle 13 as shown in FIG. 6 isdistinguished from valve needle 13 shown in FIG. 3 by its tripartitenature. In this exemplary embodiment of valve needle 13, armature 17 andvalve closure element 18 are joined to one another by a sleeve-likejoining part 50.

Valve closure element 18 is again provided immovably on valve needle 13,by way of weld be ads 63 in the manner described above, but in this casenot to armature 17 but rather to joining part 50 which now serves as theclosure element support. All statements regarding the deformation ofsegment 48 on closure element support 17 in the example according toFIG. 2 are entirely transferrable to joining part 50 according to FIG.6, since the geometry and function are comparable.

In addition to the configuration of closure element support 17, 50 as aturned part or cold-pressed part, embodiments as a sintered part ormetal injection-molded (MIM) part are also possible.

It should be mentioned that while the spherical shape of valve closureelement 18 is particularly preferred because of its ease of centering,it is nevertheless not exclusive. Indeed, valve closure elements 18having a cylindrical shape with a spherical polished portion (FIG. 7), acylindrical shape with a conical tip (FIG. 8), a cylindrical shape withtwo opposing conical tips (FIG. 9), a semi-spherical shape, and soforth, can also be attached to closure element support 17, 50.

What is claimed is:
 1. A fuel injection valve, comprising: a magnetcoil; a core at least partially surrounded by the magnet coil and havinga longitudinal valve axis; a fixed valve seat; and an axially movablevalve needle at least partially surrounded by the core and including atleast one closure element support and a valve closure element, the valveclosure element being immovably joined to the at least one closureelement support and coacting with the fixed valve seat, and the at leastone closure element support having an inner longitudinal bore extendingto a surface of the valve closure element, wherein: an end of the atleast one closure element support facing the valve closure elementincludes a contour that deviates from an annular profile such that atleast two flowthrough openings in communication with the innerlongitudinal bore are formed between the at least one closure elementsupport and the surface of the valve closure element.
 2. The valveaccording to claim 1, wherein the contour of the end of the at least oneclosure element support facing the valve closure element has atriangular profile.
 3. The valve according to claim 1, wherein thecontour of the end of the at least one closure element support facingthe valve closure element has a pentagonal profile.
 4. The valveaccording to claim 1, wherein a downstream end of the at least oneclosure element support includes corner regions and edge regions in anequal number, the number of corner regions and edge regionscorresponding to a number of the at least two flowthrough openings. 5.The valve according to claim 4, wherein each edge region is anattachment region for the valve closure element on the at least oneclosure element support.
 6. The valve according to claim 5, wherein thevalve closure element is immovably joined to the edge regions by way ofweld beads.
 7. The valve according to claim 1, wherein an outerperiphery of the valve closure element includes a plurality of flattenedareas.
 8. The valve according to claim 1, wherein the at least oneclosure element support is formed as an armature.
 9. The valve accordingto claim 1, further comprising: an armature; a joining part serving asthe at least one closure element support and joining the armature andthe valve closure element.
 10. The valve according to claim 1, whereinthe at least one closure element support corresponds to one of a turnedpart and a cold-pressed part.
 11. The valve according to claim 1,wherein a configuration of the valve closure element is spherical.
 12. Amethod for manufacturing a valve needle of a fuel injection valve,comprising the steps of: providing a metal closure element supporthaving: an inner longitudinal bore, a circular cross section, and acircular outer contour; providing a valve closure element; using atleast one deformation tool to plastically deform an end of the metalclosure element support that is to face toward the valve closure elementsuch that the metal closure element support includes at the end that isto face toward the valve closure element a contour that deviates from anannular profile, the metal closure element including a plurality ofcorner regions and a plurality of edge regions; and subsequent to thestep of using the at least one deformation tool, attaching the valveclosure element to the deformed end of the metal closure elementsupport.
 13. The method according to claim 12, further comprising thestep of: attaching an armature on a side of the metal closure elementsupport located opposite to the valve closure element.
 14. The methodaccording to claim 12, further comprising the step of performing one ofthe steps of: engaging the at least one deformation tool in the innerlongitudinal bore, and engaging the at least one deformation tool on anouter periphery of the metal closure element support.